DA* AF problem - diagnostic opinions welcome

Stan Halpin stan at stans-photography.info
Tue Oct 27 22:44:02 EDT 2009


On Oct 27, 2009, at 6:22 AM, Leon Altoff wrote:

> Hi Stan,
>
> It could very easily be a problem with your K20...
> the camera and lens need to go in together for service...
> Look upon it as an excuse to get a K7 while the 20D is in for the  
> service :)
>
> Leon
>
> 2009/10/27 Stan Halpin <stan at stans-photography.info>:
>> The lens in question: DA* 300/4.
>>
>> Basic symptom - it does not autofocus on my K20.
>> Expanded description - sometimes it works when first turned on, but  
>> then
>> refuses to work when woken up after a Sleep period.
>>
>> "Doesn't work" = nothing happens. It is not mis-focusing, it is  
>> rather doing
>> nothing - no response to shutter depression or AF button.
>> Expanded description of "doesn't work" = not only will it not  
>> autofocus, but
>> I cannot manually focus either. Focus rings turns but nothing  
>> changes.
>> I tried another DA* lens (50-135) and it works flawlessly.
>>
>> OK, simple issue, right? Lens needs repair.
>>
>> So, when it isn't working,  I switch the lens, on the lens barrel,  
>> to MF. I
>> still cannot focus!
>> So, I also switch the AF/MF switch on the body to MF, and then I  
>> regain
>> (manual) control.
>>
>> All pretty definitive so far, it seems that it must be a lens  
>> problem, and
>> off to Pentax with it.
>>
>> But when I use the same lens on a second K20, no problem. It works  
>> as it is
>> supposed to.
>>
>> Dirty contacts on the lens and/or first body? I cleaned those; no  
>> change in
>> the lens (mis)behavior.
>>
>> Any suggestions as to what is going on?
>>
>> stan
>>
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